1. Field of the Invention
The present invention relates to a cadmium free bug lamp. More particularly, the present invention relates to a yellow bug lamp comprising an electric light source enclosed within a vitreous, light transmissive envelope with a cadmium free coating deposited on the surface of the envelope.
2. Background of the Disclosure
Bug lamps comprising conventional incandescent lamps which emit a yellow color when energized are well known and old to those skilled in the art and to the consumer. Such lamps find use in both indoor and outdoor environments where the presence of both flying and crawling insects is a problem. Conventional incandescent lamps attract insects due to a significant amount of transmission in the near ultraviolet (UV) portion of the electromagnetic spectrum having a wavelength generally ranging between about 300 nm-400 nm. That region of the electromagnetic spectrum which is most attractive to a wide variety of nocturnal insects such as moths, leaf hoppers, May flies, caddis flies, various beetles, midges, mosquitoes and the like is in the near UV (310-380 nm) region of the spectrum. Incandescent lamps which emit a yellow colored light have been found to have minimal attraction for various insects while at the same time provide a reasonable amount of visible light illumination for various uses such as over entrance ways, patios, porches and the like. Such lamps generally comprise a glass envelope enclosing a filament within and terminating at one end in a conventional metal screw base, with the interior or exterior surface of the glass envelope containing an inorganic pigment coating which includes cadmium sulfide as the main pigment for emitting a yellow colored light. Some lamp manufacturers apply such coatings electrostatically as a dry powder to the interior surface of the glass lamp envelope whose wall is given a positive potential with respect to the powder. Electrostatic forces cause the powder to adhere to the interior surface or wall of the glass envelope. An incandescent lamp of this kind is disclosed in, for example, U.S. Pat. No. 3,320,460. At least one lamp manufacturer applies an enamel coating containing such pigments to the exterior surface of the glass envelope. In either case, the coatings must be resistant to the heat generated by operation of the lamp.
Recently, cadmium and cadmium containing compounds such as cadmium sulfide yellow pigments have been declared to be hazardous materials with respect both to workers who are exposed to such materials and also to the environment with respect to disposal of waste containing cadmium and cadmium containing compounds. As a result, there is now a world-wide drive on to decrease the use of such cadmium containing compounds and most countries have enacted laws to restrict such use. Accordingly, there is a compelling interest in eliminating or at least reducing or minimizing the amount of cadmium in lamps, including the yellow colored bug lamps which employ cadmium sulfide as all or a portion of the yellow pigment. One attempt to minimize the amount of cadmium present in a coating used for bug lamps is disclosed in U.S. Pat. No. 4,633,127 wherein the amount of cadmium in the coating is reduced by up to about 50-60%. However, a significant amount of the coating is still a cadmium containing pigment. Accordingly, there is a need to still further reduce and preferably even eliminate altogether cadmium compounds from coatings employed in yellow bug lamps.